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Are Your Vitamin D Levels Dropping With The Sun?

bone health Nov 05, 2023

The recent daylight saving time change serves as a good reminder to pay attention to your vitamin D levels. 

Vitamin D is an essential nutrient that most of us just don't get enough of. Low levels are associated with an increased risk of bone loss, fractures, muscle weakness, compromised immune function, mood dysfunction, and other issues.

Research shows that the shift to daylight savings in the spring and fall is associated with drops in vitamin D levels of up to 10-20%. The decrease in sun exposure affects vitamin D synthesis, especially after the spring transition. Read on to learn more about this crucial nutrient.

The Key Need-to-Know Facts on this crucial nutrient: Vitamin D3

  • Sun exposure allows our skin to synthesize vitamin D3, but production drops in winter at high latitudes. Supplements are often needed, especially in winter.
  • Fatty fish, fish oils, liver, and egg yolks are top food sources. Milk and mushrooms also provide vitamin D3.
  • Vitamin D3 aids calcium absorption and bone mineralization. Deficiency contributes to osteoporosis.

  • Older adults, those with dark skin, people who are overweight, and those with absorption issues are at high risk for deficiency.
  • Blood levels below 30 ng/mL are considered deficient. Optimal is 40-60 ng/mL for full health benefits.

  • Very high doses of over 10,000 IU daily may cause excess calcium absorption.  Hypercalcemia can lead to kidney stones, bone loss, kidney damage, nausea, fatigue, and arrhythmias if unchecked.

  • The upper limit is 100-150 ng/mL in blood. Toxicity risk increases above that threshold.

  • Excess vitamin D is rare, BUT blood levels should be monitored with high-dose supplementation.

Be Safe - Get Tested, Know Your Ranges and Your Target Levels:

  • Talk to your doctor about your Vitamin D status, ask to be tested, and follow up on the results.

  • If not covered by insurance, it will generally run $50-$100, but well worth the investment. 

  • 25-hydroxyvitamin D blood test is the best way to measure your status.

  • Target Result Ranges:

    Below 30 is deficient.
    30-50 ng/mL is the optimal range.
    Above 150 ng/mL can be TOXIC.
  •  Some experts recommend levels around 60 ng/mL for maximum immune health and cancer prevention.

Other Quick Tips:

  • Spend 5-30 minutes in the midday sun regularly to encourage vitamin D synthesis.
  • Eat oily fish 2-3 times per week and consider cod liver oil capsules.
  • Check labels and choose vitamin D-fortified milk, yogurt, and cereal, and enjoy lots of leafy greens and mushrooms.
  • Get blood tested to verify optimal 25-hydroxyvitamin D level
  • If needed, under a doctor's supervision, take a high-quality D3 supplement of 1000-5000 IU daily, or 50,000 IU weekly.  
  • After 3-4 months of supplementation, retest blood levels to confirm optimal range.

  • Get your vitamin D levels tested, especially at the end of winter.

My Personal Protocol:

Caveat for the statements below about my personal protocol: we are all unique, different ages, sizes, health status, etc. I am not a doctor, nor is the information to be construed or used as medical advice or a personal recommendation, please consult your healthcare professional related to your own personal requirements. Your situation will likely be different. 

Because I am often asked about my personal protocol,  I will share as a point of reference based on the caveat above:

  • As a post-menopausal woman of normal weight, my doctor shoots for me to maintain between 85-90 ng/mL year around. I live in the Northern Hemisphere, near the 40 parallel - winter sunlight ranges from the lowest of 6.5 hours to 8 hours during the high winter months.

  • I get tested every October and May, and the results have been pretty predictable over the last 6 years.

  • Based on my results and my doctor's recommendation, I use Ortho Molecular Vitamin D3 capsules in 50000 IU strength, taken only once a week, from October to May.  It’s a convenient and inexpensive option that helps me maintain my health. 

  • I started this protocol at age 50 just as menopause hit. This along with lifting weights 5 days a week has been quite effective. My bone density test results show the bone health of a 35-year-old menstruating woman.  (✨I'll take it, minus the red dot days!)

There is a lot more to say about all of this. But whichever side of menopause you find yourself, don't overlook the importance of vitamin D for your long-term bone health and disease prevention.

Action Step:

Make it a priority to talk to your healthcare provider about Vitamin D3 testing and supplementation to keep your levels where they need to be. 


  1. NIH overview of vitamin D -
  2. BMJ systemic review on vitamin D and bone health - 
  3. Research on optimal vitamin D levels -

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